JPH02811A - Camera with automatic focusing function - Google Patents

Abstract

PURPOSE:To reduce possibility that a shutter chance is missed and to take a picture which is almost focused by continuing follow-up operation by means of assuming that a current defocus amount is zero if it is abnormal or unknown. CONSTITUTION:In case a moving body lies outside a focal point detecting area due to hand shaking, etc., the defocus amount detected by a focal point detecting means 1 becomes greater than a prescribed value, or the means 1 fails to detect a focal point. In such a case, the current defocus amount goes to abnormal or unknown, however, it can be assumed to be zero because the camera is focused on an object owing to follow-up operation. Then, a lens driving amount calculating means 3 calculates a lens driving amount and continues driving a lens. As a result, a focused state can always be maintained unless the moving speed of a main object remains unchanged.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a camera with an automatic focus adjustment function, and is particularly suitable for an AFL reflex camera.

(Prior art) Conventionally, in cameras with an automatic focus adjustment function, when the previous and current defocus directions are the same, it is determined that the subject is moving, and tracking control is used to drive the lens in accordance with the speed of the subject. However, this conventional example does not disclose countermeasures when the current focus detection result is abnormal or unknown. Not yet.

(Problems to be Solved by the Invention) Cameras with an automatic focus adjustment function are basically equipped with a one-shot AF mode in which focus adjustment is locked when focus is first achieved. This one shot AF
When using this mode, focus priority release mode is often used in which the shutter is not released until focus is achieved. By the way, even when using focus priority release mode in one-shot AF mode, it is still necessary to may be out of focus. This is because, for example, when the subject is moving in the direction of distance, the subject will deviate from the in-focus position by the time the camera is released.

Therefore, as in the conventional technology described above, when focus detection is performed multiple times and the subject is determined to be a moving subject (dynamic subject), the moving speed of the subject is calculated, and the current defocus amount and the subject's distance are calculated. It has been proposed to adopt a tracking mode in which the focus position at the next time of focus detection is predicted from the movement speed and the lens is driven to the expected focus position. If this follow-up mode is used, the focus detection result after driving the lens should be such that the amount of deflation is almost zero. However, if the moving object moves out of the focus detection area due to camera shake or the like of the photographer, the amount of defocus may become significantly large or the focus may become impossible to detect. When a release request is made in such a case, since the current defocus amount is abnormal or unknown, correct follow-up control cannot be performed, and there is a risk of missing a photo opportunity.

The present invention has been made in view of the above points, and its purpose is to provide a camera with an automatic focus adjustment function that has a tracking mode that drives the lens according to the moving speed of the subject. To reduce the risk of missing the object and to always be able to take photographs that are close to being in focus.

(Means for Solving the Problems) In order to solve the above problems, the present invention detects the focal state of the lens with respect to the subject to be focused on, as shown in FIG. A focus detection means (1) that outputs a signal indicating the focus amount, a movement speed calculation means (2) that calculates the moving speed of the subject using the defocus amount of multiple times, and a movement speed calculation means (2) that calculates the moving speed of the subject using the current defocus amount and the movement of the subject. Lens drive amount calculation means () that calculates the lens drive amount to make the defocus amount zero at the next focus detection from the speed.
3) and a lens drive means (4) that drives the lens according to the lens drive amount, the lens drive amount calculation means (3) calculates the amount of defocus detected by the focus detection means (1). is larger than a predetermined value, or when focus detection by the focus detection means (1) is impossible, the current defocus amount is set to zero and the lens drive amount is calculated. .

The focus determining means (5) determines whether or not the subject is in focus based on the focus detection result of the focus detecting means (1), and the focus determining means (5) issues a release request when it is determined that the subject is in focus. It is preferable to further include release permission means (6) for permission.

However, FIG. 1 is an explanatory diagram showing the configuration of the present invention in functional blocks, and in the embodiments described later, all or part of means (1) to (6) are implemented by a microcomputer program. It has been realized.

(effect) Hereinafter, the operation of the present invention will be explained with reference to FIG.

The focus detection means (1) detects the focus state of the lens with respect to the subject to be focused, and outputs a defocus amount DF indicating the focus state. This defocus jiDF
is a signal whose magnitude represents the amount of defocus, and whose sign indicates the direction of defocus. Movement speed calculation means (
In 2), the moving speed V of the subject is calculated using multiple defocus amounts.

From the moving speed of this subject and the current amount of defocus,
The lens drive amount calculation means (3) calculates the lens drive amount to make the defocus amount zero at the next focus detection. Depending on this lens drive amount, the lens drive means (
4) drives the lens.

By the way, if a moving object moves out of the focus detection area due to camera shake of the photographer, the amount of defocus detected by the focus detection means (1) may become larger than a predetermined value, or the focus detection means (1) may fail to detect the focus. It may be possible. In such a case, the current defocus amount is abnormal or unknown; however, in the present invention, based on the idea that the main subject should be in focus due to tracking control, the current defocus amount is abnormal or unknown. Assuming that the defocus amount is zero, the lens drive amount calculation means (3) calculates the lens drive amount, and continues the lens drive. Therefore, as long as the moving speed of the main subject does not change, the in-focus state can always be maintained.

Since the present invention operates in this way, even if the current focus detection is abnormal or impossible, it is possible to respond to the release request while continuing tracking control, so there is less risk of missing a photo opportunity and the focus is always on point. It is possible to take close-to-focus photos.

Note that although the present invention is based on the assumption that the release request is always permitted, a focus determination means (5) and a release permission means (6) are further added, and the blackness determination means (5) determines whether the focus is in focus. If it is configured so that the release request is permitted by the release permission means (6) if it is determined that the camera is in focus, it is guaranteed that the photographed photograph will always be in focus.

More detailed configuration and operation of the present invention will become clearer in the following description of embodiments. In the embodiment, the lens drive amount calculation means (3) is realized by step #71 in FIG. 8, and when the current defocus amount is abnormal or unknown, the current defocus amount is set to zero. The settings are #76, #77, and
This is achieved by step #89. Further, step #95 in FIG. 9 realizes a moving speed calculation means (2).

(Embodiment) FIG. 2 is a block diagram showing the hardware of a camera according to an embodiment of the present invention. In FIG. (22) is a CCD image sensor for AF, and the integration start signal φI is sent from the microcomputer (21).
When c(2 is received, integration is started, and after the integration is completed, the output of each pixel is A/D converted and sent to the microcomputer (21).

The microcomputer (21) performs calculations based on the output of each pixel transmitted from the CCD image sensor (22), and calculates the amount of defocus of the subject image. After calculating the amount of defocus of the subject, the microcomputer (21) drives the lens to make it zero. Here, the conversion coefficient that indicates the relationship between the amount of lens drive and the amount of defocus differs depending on the lens. Therefore, the conversion coefficients are stored in a lens circuit (25) built into each lens. The microcomputer (21) reads the value of the conversion coefficient from the lens circuit (25), and calculates the number of pulses required to drive the lens by multiplying the calculated defocus amount by the conversion coefficient k. The microcomputer (21) is the AF for driving the lens.
The calculated number of pulses is sent to the motor control unit (23), and the AF motor control unit (23) controls the AF for driving the lens.
The motor (24) is driven by the number of pulses transmitted from the microcomputer (21).

(26) is a display section, which displays the figure shown in FIG. In FIG. 3, the LED (26A) displays in-focus or out-of-focus status. In other words, if the defocus amount is calculated and the lens is in focus after the lens is driven, the L
The ED (26A) lights up in green to notify the photographer of focus. Further, if the defocus amount is not calculated for a reason that will be described later, the LED (26A) flashes in red to notify the photographer that focusing is not possible. In addition, LED (26
B) and (26C) are displays showing switching of the photographing mode of the camera in this embodiment. When the subject is stationary, the focal position after focusing is fixed, photography is performed in focus lock mode, and the LED (26B) is lit. On the other hand, if the subject is moving, the tracking mode is used to follow the subject's movement and always maintain focus, and the LED (26C) lights up.

In FIG. 2, (Sl) is a switch that is turned ON when a release button (not shown) is pressed down to the first stroke. When the switch (Sl) is turned ON, interrupt processing by the interrupt board (INTI), which will be described later, is executed.
AF operation is performed. Further, (S2) is a switch that is turned on when the release button is pressed down to a second stroke, which is deeper than the first stroke. switch (S2) is O
When it reaches N, interrupt processing by an interrupt port (INT2>, which will be described later) is executed, and a release operation is executed.

Interrupts by this interrupt port (INT2) may be prohibited by a program. Therefore, the switch (S2) is also connected to the input port (IP2) of the microcontroller (1), and even when interrupts by the interrupt port (INT2) are prohibited, the microcontroller (21) is connected to the input port (IP2). By scanning the camera, it is possible to determine whether or not the photographer has made a release request. (S3) is a mirror up switch. This switch is used to raise the mirror (not shown) inside the camera body so that the photographer can observe the light that has passed through the photographic lens through the viewfinder. In order to allow the light that has passed through the photographing lens to reach the film surface during exposure, this is a switch that is turned ON when the camera is completely removed from the photographing optical path.
By charging, it will be reset to OFF state.

(27) is an LED that emits infrared light (auxiliary light) to irradiate the subject when the brightness of the subject is low, and is controlled by an auxiliary light control section (28). When the microcomputer (21) determines that the brightness of the subject is low, it activates the auxiliary light control unit (28).
), outputs an auxiliary light emission signal to the CCD
The precision start signal φIcc is sent to the image sensor (22).
is output, and when the integration is completed, the auxiliary light control section (28
) stops the auxiliary light emission signal that was being output.

As a result, the CCD image sensor (22) performs CCD integration using the auxiliary light when the brightness is low. (29) is a timer for calculating the rate of change of the focal position for a dynamic subject, which will be described later. The timer value TM is cleared to zero when AF is started by turning on Sl), and then the timer value TM increases steadily, making it possible to monitor the time since AF start. end.

Next, we will explain the algorithm of this embodiment. In this embodiment, it is possible to distinguish between a stationary subject and a moving subject, and automatically switch between two shooting modes: "focus lock mode" and "following mode". I have to. Each shooting mode will be outlined below.

First, select [Focus Lock Mode] as the shooting mode.
If you have set
The amount of defocus of the subject image in this focus frame is determined, and the lens is driven so that the subject image is brought into focus. During general photography, there are many cases where the photographer wants to frame the subject so that it is located in a different location from the focus frame in the viewfinder.In such cases, first,
The photographer moves the lens so that the subject he or she wants to focus on is within the focus frame, and then
After performing the motion, it is necessary to perform framing without changing the focal point position. The "focus lock mode" is a mode in which, in such a case, the release is performed without changing the focal position after focusing.

In this embodiment, a "following mode" is provided as another photographing mode. This is a shooting mode that corresponds to a case where the subject that the photographer wants to shoot is moving. When the subject is moving, the amount of defocus of the subject detected on the focus frame changes every moment. There is no problem if this change is small enough to fall within the depth of field on the film surface, but if the change in defocus exceeds the depth of field, the constantly changing defocus In the six embodiments in which it is necessary to follow the subject in order to change the focal position from moment to moment according to the movement of the subject, the "following mode" is set when the subject moves in this way, and the image formation of the subject image changes from moment to moment. It constantly tracks the position and maintains focus at all times. In addition, when the photographer presses the release button, "Following mode" takes into consideration the time lag between the timing of pressing the release button and the timing of the shutter curtain actually running and exposing the film surface. Also included is a predictive control method in which the amount of defocus is predicted and the lens is driven so that the subject image is in focus at the timing of exposure on the film surface. This “following mode”
With this feature, it is possible to always obtain in-focus photos even when the subject is moving.

This will be explained in detail below using a detailed flowchart.

When the release button is pressed down to the first stroke, the switch (
SL) is turned on, the AF start flow shown in FIG. 4 is executed. In the following explanation, the symbol “#
” shall mean a step in the program. #1
By disabling interrupts from the interrupt port (INT2), the release routine is prevented from being called even if the release button is pressed down to the second stroke and there is a release request. Subsequently, in #2, the microcomputer (21) inputs a conversion coefficient (k) for converting the defocus amount into the number of pulses for driving the lens from the lens circuit (25) shown in FIG. Next, #3
A timer (29) for monitoring the distance measurement time described later.
) is being reset. Furthermore, focus detection calculation is performed in #4.

FIG. 11 shows a subroutine for focus detection calculation, #1
At #08, the timer value TM is read, and at #10, the start time of CCD integration, which will be described later, is stored in the memory in the microcomputer (21) as a memory value TM'. Subsequently, in #110, a low brightness flag is determined. When the brightness of the subject is low, the CCD image sensor (22) is not irradiated with sufficient light, so the above-mentioned auxiliary light is irradiated onto the subject.
The necessity of the auxiliary light irradiation is determined using the low brightness flag. A
Immediately after F start, the low brightness flag is cleared, so #111 auxiliary light emission is skipped, and #112 C
The CCD image sensor (22) that performs CD integration is an image sensor for obtaining object information for performing focus detection calculations, and by performing integration, brightness information of the object is accumulated in each pixel. In #113, the data of each pixel in the CCD image sensor (22) is sent to the microcomputer (21).
) data dump processing is performed. Below, #1
The correlation calculation, interpolation calculation, and focus shift pitch calculation in steps 14 to #116 are one or more processes that represent the flow of a well-known focus detection calculation, and are performed in the focus detection calculation subroutine in #4.

When the focus detection calculation is performed in #4, if the reliability of the result is poor, focus detection becomes impossible.

Make the determination in #5. If focus detection is not possible here, proceed to #501; otherwise, proceed to #501.
Proceed to step 11. If you proceed to #501, check whether the brightness is low or not. First, before the focus detection calculation,
When the CCD is used for 11 minutes, the auxiliary light is not emitted, so the subject brightness is low and focus detection may not be possible. If it is determined that the brightness is low in #501, and the low brightness flag is not set in #6, proceed to #7, set the low brightness flag, and return to #4. This time, the auxiliary light is emitted and the COD On the other hand, if low brightness was not determined in #501, or if the low brightness flag was set in #6 and CCD integration was performed using fill light, the contrast of the subject image is determined to be in a low contrast state.

In this case, proceed to #8. In #8, it is determined whether or not a low contrast scan has been performed in the past by re-editing the focus detection calculation while scanning the lens position. However, if this routine is entered for the first time, , No is determined in #8,
Start low contrast scan in #9. If the low contrast scan has already been completed in #8, a low contrast display is performed in #10 to notify the photographer that focus detection is impossible. This is done by flashing the LED (26A) shown in FIG. 3 in red.

If it is determined in #5 that focus detection is possible, the process proceeds to #11. In #11, a low brightness flag is determined. The above-mentioned CCDf1 is used when using and not using the auxiliary light.
Since the minutes and hours are different, the sampling period T when repeatedly calculating the defocus amount as described later. need to change. This lick, #12. In #13, each sampling period T0 is set. In #14, the defocus amount is calculated from the result of the focus detection calculation. In #15, it is determined whether the defocus amount is within the focusing range, and if it is within the focusing range, the process proceeds to the AP mode determination routine from #441 onwards, and if the defocus amount is outside the focusing range. #16
Proceed to the subsequent flow 0 Normally, the position of the lens is not fixed at the time of AP start, so it is rarely within the in-focus range, and the process proceeds to #16 and beyond.

In #16, the number of pulses for driving the lens is calculated using the defocus amount calculated in #14 and the conversion coefficient input in #2. Subsequently, the lens is driven in #17, and the lens is driven by the number of pulses calculated in #16. After this, a routine for detecting the state of the subject is entered.

In #18, the counter CN is cleared to zero. This counter CN is a counter for counting how many times focus determination has been performed in the routine after #19.

In subroutine #19, focus detection calculation is performed again. If the focus cannot be detected in #20, repeat #19 until the focus is detected.If the focus is detected, #21
The defocus amount is calculated in #22, the value of the counter CN is incremented by one, and the focus is determined in #23. At this time, if the subject is stationary, or if the focus position changes slowly even if it is moving, the defocus amount calculated in #21 is within the focusing range, and the process proceeds to #24, where the counter CN is If the value of , is 1, that is, if the focus is achieved with one lens drive in #17, then A after #441
Proceed to the P mode determination routine.

However, if it is not in focus in the focus judgment in #23, it is assumed that the focal position of the subject image has changed during lens driving, or that the focus detection accuracy is low and the amount of defocus is inconsistent. , proceed to the routine after #30.

#30. If the value of the counter CN is 1 in #31, the lens has been driven once in the past, and after calculating the number of pulses for driving the lens again in #41, the lens is driven in #42. After this, After waiting time in #43, #1
Repeat the steps from 9 onwards.

The reason for waiting for time here is that when detecting the moving speed of a subject whose image focal position changes over time using the method described below, if the time interval between focus detection is short, the speed detection will be accurate. This is because it is not done well. In subroutine #19, the CCD integration start time TM' is set by the microcomputer (21).
Since the timer value TM is stored in the internal memory, a time wait is performed in #43 until the timer value TM reaches TM≧T0+TM'.

After repeating the calculations in #19 to #22, focus determination is performed again in #23.

If focus is determined in #23, the value of counter CN is 2.
Therefore, in #24, it is determined that CN is not 1, and in #25, the input port (IP2) of the microcontroller (21) is determined.
) to determine whether there is a release request.

Here, if there is no release request, proceed to the AF mode determination routine; if there is a release request, proceed to the AF mode determination routine.
In order to quickly respond to this request, the process proceeds to the release routine after performing steps #26 to #29. In step #26, the sign of the defocus IDFb obtained last time and the sign of the defocus i D F a obtained this time are determined. Determine whether they are equal or not. If the signs of the defocus amounts DFa and DFb are the same, it means that the focal position of the subject image shifts in the same direction. Therefore, if the previous defocus amount DFb and the current defocus amount DFa have the same sign, the subject is moving. After calculating the speed ■ in #27, set the tracking mode flag to follow the movement of the subject in #28.
Press #2 to enable release and enter the release routine.

In calculating the subject speed in #27, the defocus i D Fa calculated this time is divided by the time interval (ta - tb) between the current and previous focus detection, and the value is further multiplied by (1/2>). This is done by reducing the subject speed by 1/2 to avoid estimating the expected subject speed V higher than the actual amount when there is variation in the calculated defocus amount.
This is because the calculation is performed with a weight of 2. Actually, since the defocus amount D Fa is within the focusing range this time, the moving speed of the subject is not so large, and this is sufficient for the following speed.

On the other hand, if the signs of the current defocus amount DFa and the previous defocus amount DFb are opposite in #26, it means that the focal position of the subject image has shifted in the opposite direction, so it is not possible that the subject is moving in the same direction. It is not recognized and the release operation is performed without tracking.

Next, if it is out of focus when the value of the counter CN is 2 in the focus judgment in #23, then in the judgment in #30, #37
Processing moves to In #37, the signs of the current defocus amount DFa and the previous defocus amount 1DFb are compared.

Here, if the signs are the same, it is determined that the subject is moving in the same direction, and the process proceeds to #38. If the signs are opposite, it is not determined that the subject is moving in the same direction, so the lens drive In #38, it is determined whether there is a release request or not. If there is a release request, the subject speed V is calculated in #39. In #40, the tracking mode flag is set and the tracking is performed. Proceed to mode routine, #
In the speed calculation of No. 39, the current defocus amount DFa is divided by the focus detection time interval (ta-tb), and then (1/2
) is doubled. This is the same as the previous case, but here, the defocus amount DFa is outside the focusing range,
Because the subject's speed ■ is large, we do not immediately proceed to the release operation, but instead enter the tracking mode described later, where we accurately calculate the subject's speed ■ before starting the release routine.
-It is designed to fit inside.

On the other hand, if there is no release request in #38, proceed to #41, calculate the number of pulses for driving the lens, drive the lens in #42, proceed to #43, and repeat the processing of #43 to #22. After that, the focus is determined again in #23. If it is in focus, proceed to #24 and below, and if it is out of focus, the value of counter CN is 3. , #30° #31 are all determined to be No, and #32
If the signs of the three defocus amounts match in #32, it is determined in #33 whether the absolute values of the three defocus amounts are all within 1 ran. There is. If the absolute value of the defocus amount exceeds 1 mm, there is a high possibility that the distance was measured for another subject, so proceed to #41 and onwards and repeat focus detection again.
#32. If #33 is YES, it is determined that the focus detection of the subject was normal all three times and that the subject is moving in the same direction, and the velocity V = (DFa - D) is determined in #34.
After calculating Fb)/(ta-tb), the follow-up mode flag is set in #35, and the process shifts to follow-up mode. In addition, if the three defocus amounts do not have the same sign in #32, it is determined in #36 whether the signs of the current defocus amount DFa and the previous defocus amount DFb are the same, and in #36
If the signs of the current defocus i D Fa and the previous defocus amount DFb match, #41. #42
After driving the lens again, proceed to step #43 and subsequent steps to repeat the subject discrimination. Also, if the signs of the current defocus amount DFa and the previous defocus amount DFb do not match in #36, focus detection It is determined that the accuracy is low and the amount of defocus varies, and the system enters average mode ■.

FIG. 10 shows the flow of average mode H. #9
9, the defocus amount DF is the average value DF- of the current defocus 31 D Fa, the previous defocus amount DFb, and the previous defocus it D F c.
(DFa+DFb+DFc)/3 is calculated. #1
00 determines whether this defocus amount DF is within the focusing range, and if it is in focus, the focus is displayed in #101, the release is permitted in #102, and then the average mode l
to move to. In average mode I, #66 in Figure 7
After setting the average correction flag as in #67, a focus lock display is performed and the camera waits for release.

On the other hand, in #100, there are large variations in each defocus amount, and the average defocus amount may exceed the focusing range. In this case, the number of pulses for driving the lens is calculated in #103, the lens is driven to a predetermined position in #104, and then focus detection calculation is performed again in #105. #10
If focus detection is not possible in step 6, repeat the focus detection calculation in #105 until focus is detected.If focus is detected, calculate the defocus amount in #107, and then repeat step #99.
Return to #9 until the average defocus amount is within the in-focus range.
Repeat steps 9 to #107.

As described above, after calculating the amount of defocus, the lens is driven to the expected focus position, and if it is not in focus, the movement speed of the imaging position of the subject image is fast and the lens drive cannot catch up, or the defocus Since the accuracy of the amount calculation is low, we have described a method of determining whether the defocus amount is either tracking mode or average mode by assuming that the amount of defocus is varying. At the same time, the sequence when a release request occurs during determination has also been described.

If the subject is moving quickly, the tracking mode can be determined using the method described above, but if the subject is slow, it is possible to determine whether the subject is moving out of the focus zone or not, even if there is a time lag caused by driving the lens to the intended focus position. First, it may be determined that focus is achieved in #23. Therefore, even after the focus determination in #23, the tracking mode is determined in the AF mode determination routine from #441 onwards. This AF mode determination will be explained below.

In #441, a flag (A F M F ) indicating that the AF mode determination routine has entered is set. #4
In step 4, a focus display is performed to notify the photographer that the subject is in focus. In addition, when focusing, the prohibition of interrupts by the interrupt board (INT2) is canceled, and the release is always activated.
When a release request is made, a release operation is performed immediately. Subsequently, the counter CN 2 is cleared in #46. The counter CN z indicates the number of focus detections for determining the AF mode. Focus detection calculation is performed in #47, and if it is determined that focus cannot be detected in #48, the contrast of the original subject is low, or There may be a case where focus detection calculation is performed on another subject whose focus position is significantly different from that of the subject to be photographed after focusing, and the process proceeds to #55. If the focus is detected normally in #48, calculate the defocus tDF in #481. If IDF > 1 m + self in #49, after focusing, calculate the subject to be photographed and the focal position. Since it is considered that focus detection has been performed on another subject with a different value, the process proceeds to #55. In #55 to #57, processing is performed when such an irregular focus detection calculation is performed. In #55, first, the previous ignore flag is checked. The previous ignore flag is a flag for determining whether or not irregular focus detection has been performed continuously. Initially, this flag is reset, and # 55 is No, and the process proceeds to #56. #
56, when the next irregular focus detection is performed,
The previous ignore flag is set so that #55 is YES. If YES in #55, it means that incorrect focus detection has been performed twice in a row, and in this case, a flag (A F M F) is reset, focus lock is displayed in #57, and the camera waits for release.

Here, the reason why focus detection is performed only when irregular focus detection is performed twice in a row is as follows.

When photographing a moving subject in tracking mode, it is necessary to always follow the subject within the focus frame, but the subject may deviate from the focus frame due to camera shake or the like.

Therefore, if an incorrect focus detection is performed once, it is ignored. However, if this happens twice in a row,
It is determined that the photographer intentionally moved the subject out of the focus frame. This is because in focus lock photography, the photographer shakes the camera to decide on the composition after focusing on the subject. Therefore, if incorrect focus detection is performed twice in a row, focus lock mode is determined as AP mode, focus lock is displayed, and the camera waits for release.

#48. If the determination in #49 is No, it is determined that the subject has not changed and the amount of defocus has been calculated reliably, and the process proceeds to #50, where the previous ignore flag is checked. Here, if the previous ignore flag was set, it means that the normal focus detection calculation was not performed last time, and in #51, by calculating the average of the defocus amount DFc from the time before last and the defocus amount M D Fa this time. It is calculated by interpolating the previous defocus amount DFb. Next, in #52, the previous ignore flag is reset, and the process proceeds to #53.On the other hand, if the previous ignore flag was not set in #50, there is no need for interpolation, so the process directly proceeds to #53.In #53, the counter is reset. Count up CN2 until the value of counter CN2 reaches 4 in #54.
Repeat #47 to #54. The value of counter CN 2 is 3
In the following cases, the timer value TM changes from the memory value TM' to T in #541. Wait until the number increases.

After completing four focus detection calculations, reset the flag (A F M F ) indicating AF mode determination in #581,
The process proceeds to #58. In #58, the sign of the defocus amount for all four times is the same, and the defocus amount changes monotonically, and furthermore, in #59 to #61, two consecutive defocus amounts are detected. If it is determined that all the absolute values of the differences in amounts are equal to or higher than the predetermined determination threshold value 8, it is assumed that the subject is moving, and the camera shifts to the tracking mode. At this time, the initial velocity at the time of following is V − (D Fa − D F c)/
(ta - tc) and sets the tracking mode flag in #63 to enter the tracking mode. At this time, the speed V is calculated from the current defocus Ji D Fa and the previous defocus amount D F c because the longer the focus detection time interval (ta-tc) is, the more accurate the calculation is. ,
The newer the data, the more the initial speed when entering tracking mode.
This is because it is calculated more accurately.

On the other hand, if all four defocus amounts are not of the same sign or do not change monotonically in #58, then in #64 the stability of each defocus amount is determined by calculating the difference between the defocus amounts of the two focus detections. Determine whether the sign changes alternately or not, YE
In the case of S, it is assumed that the calculation of defocus ff1DF is unstable, and the averaging process of #65 and below is performed. In #65, the current defocus amount D Fa is used as the defocus amount.
, Previous defocus ID Fb, Previous defocus J
The average of the three defocus amounts of i D F c is set as the true defocus amount, an average neatness flag is set in #66, a focus lock display is performed in #67, and the camera waits for release. On the other hand, if the defocus amount is not changing alternately in #64, or in the determinations #59 to #61, the absolute value of the difference between successive defocus amounts is equal to the predetermined determination threshold a.
If the value is smaller than , it is assumed that the subject does not move and that the defocus amount has been calculated accurately, so no averaging processing is performed and the process proceeds to #67, where the focus lock is displayed and the camera waits for release. becomes.

This completes the description of the routine from the start of AF to the completion of AP mode determination.

Next, the sequence after entering the tracking mode will be explained. In FIG. 8, first, in step #68, a tracking mode is displayed, and then, in step #69, 2 is assigned to the counter CN3. Counter CN is used for determination when exiting from tracking mode. At #70, counters CN, CN, are cleared.

Counter CN is a counter for counting the number of times that normal focus detection was not performed in the focus detection calculation after entering the tracking mode, and counter CN is a counter for counting the number of times that normal focus detection was performed. It is. #71
Then, the moving speed of the subject ■ and the period T of focus detection calculation. The expected defocus JiD F' in the case where the lens is not driven at the next time of focus detection is calculated by adding the value multiplied by the amount DFa to the latest defocus amount DFa. Based on this planned defocus amount DF', the number of pulses for driving the lens is calculated in #72, and the lens is driven in #73.In #74, the timer value TM is changed to the memory value TM at the time of the latest focus detection calculation. Wait for a time until the value obtained by adding the focus detection period T to T for simplicity. ζTQ
', and the lens drive time is assumed to be almost nil. In the lens drive in #73, the lens is driven by the amount of scheduled defocus iDF' when the lens is not driven, so when the focus detection calculation is performed in #75, the defocus amount is calculated as approximately zero. will be done. #
At step 76, it is determined whether or not focus detection has been impossible. As mentioned above, if proper focus detection is not performed due to camera shake, etc. of the photographer, proceed to #89.
If normal focus detection is performed in step 76, defocus IDE is calculated in step #761, but if the absolute value IDFI of the obtained defocus amount is determined to be 11nI11 or more in step #77, it is determined as described above. It is determined that proper focus detection has not been performed, and the process proceeds to #89.

In #89, the current defocus filD Fa is set to zero as a result of the focus detection calculation.

This is because, as described above, the lens is driven so that the amount of defocus becomes approximately zero during the current focus detection calculation. Further, in #90, the value of the counter CN, which counts the number of irregular focus detection calculations, is incremented by one. This is so that if irregular focus detection calculations are frequently performed as described later, the tracking mode is exited at #87. #77 IDFI<I
If it is determined that Il+n+, the process proceeds to #78. In #78, the difference between the current subject position and the previous subject position is calculated as the defocus amount difference ΔDF.

FIG. 13 is a diagram for explaining a method of calculating the defocus amount difference ΔDF. In FIG. 13, the DFa origin is the lens position at the time of the current focus detection, and the DFb origin is the lens position at the previous focus detection. At the previous focus detection time tb, the lens was located at the origin of DFb, which caused the previous defocus MDFb. Previously, the defocus JiDFb' for lens driving was
The predicted movement amount of the subject is obtained by multiplying the elapsed time (ta - tb) from the previous focus detection time tb to the current focus detection time La by the subject speed V, and is obtained by adding the previous defocus 1DFb. Therefore, the current focus detection time t
At point a, the lens position has reached the DFa origin, but the subject is actually away from the predicted position, causing defocus i D Fa this time.

In this case, as is clear from the figure, the defocus amount difference ΔDF from the subject position at the previous focus detection time tb to the subject position at the current focus detection time ta is the difference between the current defocus i DF a and the previous lens drive lens. It is obtained by adding the focus JiD Fb'' and further subtracting the previous defocus and 1DFb.

In #79, this defocus amount difference ΔDF and the moving speed V
is typing a comparison of the signs. If the signs are different, it means that the subject is moving in the opposite direction to the direction calculated as the moving speed ■, and it is assumed that proper focus detection has not been performed, and the value of the counter CN is increased by one in #88. It's increasing. Furthermore, if the absolute value of the defocus amount is greater than or equal to the predetermined judgment threshold in #80, this means that the actually measured defocus amount is significantly different from the expected defocus amount, and in the above case Similarly, it is assumed that proper focus detection has not been performed, and the process proceeds to #88, #79.
．． If the determination in #80 is YES, the process advances to #81, where a counter C indicating the number of times normal focus detection has been performed is displayed.
Increase the value of N5 by one.

If the value of counter CN is not 5 in #82, #
Proceed to 87. Counter CN in #87.

A comparison is made between CN4 and CN4. Initially, the value of the counter CN3 is 2 due to the initial setting in #69, and the value of this counter CN3 is compared with the value of the counter CN, which indicates the number of irregular focus detections. That is, here, if the value of the counter CN4 is 2 or more, it is determined as YES, and the release is prohibited in #871, and the process returns to the AF mode determination, and this is repeated. Value of CN and counter CN:
This is to make it possible to exit the tracking mode by comparing the values of l.

On the other hand, if the value of the counter CN5 becomes 5 in #82, the low brightness flag is checked in #83.As mentioned above, if the low brightness flag is set, the auxiliary light is emitted. Although CCD integration is performed, it is not desirable to perform focus detection calculations indefinitely because the use of auxiliary light increases power consumption.

For this reason, the tracking mode is exited when the value of the counter CN reaches 5. If the low brightness flag is set, focus determination is performed in #91, and if it is in focus, release is permitted in #92, and focus lock display is performed in #94, and the tracking mode ends and focus is returned. Notifies the photographer that the camera is in lock mode.

If the camera is not in focus, release is prohibited in step #93 and the process returns to AF mode determination. On the other hand, when the auxiliary light is not used, the tracking mode is continued because there is no need to worry about power consumption. In #84, the value of the counter CN is incremented by one. Furthermore, #85. In #86, counters CN, CN, are cleared.

Counter CN 3 is a parameter for escaping from the follow-up mode in #87 described above. Since this counter CN3 increases according to the elapsed time (the number of focus detections) after entering the tracking mode, the conditions for exiting the tracking mode in #87 gradually become stricter. In other words, the longer the time that has elapsed since entering tracking mode, the more the subject is definitely moving, and the camera is controlled to continue tracking even if the number of incorrect focus detections increases due to camera shake, etc. .

If it is determined in #87 that the tracking mode cannot be exited, a new tracking speed ■ is calculated in #95.

In #95, in order to improve the calculation accuracy of the tracking speed ■, the difference between the current subject position and the subject position before the previous one (defocus amount difference ΔDF) is calculated as the focus detection time interval (La - t
Divide by c) to obtain the moving speed ■.

FIG. 14 is a diagram for explaining a method of calculating the defocus amount difference ΔDF. In FIG. 14, the DFa origin is the lens position at the time of the current focus detection, the DFb origin is the lens position at the previous focus detection, and the DFc origin is the lens position at the time of the previous focus detection. At the focus detection time tc before the previous time, the lens was located at the DFc origin, so the defocus fi D F c occurred the time before the previous time. The defocus amount DFc' for the lens drive before the previous time is calculated by multiplying the elapsed time E(tb tc> by the subject speed Vc from the focus detection time Lc before the previous time to the focus detection time tb the time before the previous time). It is determined in addition to the defocus amount DFc. Therefore, at the previous focus detection time tb, the lens position is D
Although the Fb origin has been reached, the subject is actually away from the predicted position, causing the previous defocus ff1D Fb. Defocus amount DFb' for previous lens drive
is from the previous focus detection time tb to the current focus detection time fl
Elapsed time until Jta (ta-tb) and subject speed vb
The predicted movement amount of the subject obtained by multiplying by the previous defocus J
Required in addition to IDFb. Therefore, at the current focus detection time La, the lens position has reached the DFa origin, but the subject is actually away from the predicted position, causing the current defocus amount DFa. In this case, the defocus amount difference ΔDF from the subject position at the previous focus detection time tc to the subject position at the current focus detection time [a] is, as is clear from the figure, the current defocus Jt D F a and the previous lens drive Defocus 1DFb' and defocus 1D for driving the lens before last
Add Fc' and further defocus ji D F
It is obtained by reducing c. That is, the defocus amount difference ΔDF is ΔDF=DFa−DFc+DFb′+DFc′.

The defocus amount difference ΔDF in the above formula is expressed as the focus detection time v
The following speed V is calculated by dividing by a(ta-tc). After this, the focus is determined in #96, and if it is in focus, the release is permitted in #97, and if it is not in focus, the release is prohibited in #98, and the process from #71 is repeated, allowing the release. In this case, if there is a release request, a release routine is called and a release operation is performed.

Finally, the release routine will be explained.

First, in #117 of FIG. 12, it is determined whether the average correction flag is set. If the average correction flag is set, the process proceeds to #121, where the number of pulses for driving the lens is calculated from the calculated defocus amount, the lens is driven in #122, and the input port ( After monitoring IP3) and confirming that the mirror is up, the lens drive is stopped in #124, and then the shutter is run. If the average correction flag is not set in #117, it is determined in #118 whether the tracking mode flag is set.

Here, if the tracking mode flag is not set to camera 1, it is determined in #125 whether or not the release was performed during the AF mode determination based on the flag (A F M F ). If this flag (AFMF) is set,
In step #126, there is a possibility that the subject is moving during the above judgment mode, so in order to correct this, the defocus amount obtained during the above judgment is averaged, and this amount is driven in step #121. For example, if two parfocal detections are performed and two defocus It(DPI, DF2) are obtained, then DF-(DPI+DF2)/2 is set. If the above flag (A F M F > is not set, lens driving is not performed and the process proceeds to #123 and onward. If the tracking mode flag was set in #118, proceed to #119.
Proceed to.

In #119, time lag τ is calculated. The time lag τ is the time from when the latest focus detection calculation is performed to when the shutter is actually moved. In #120, the value obtained by multiplying the subject movement speed V by the time lag τ is the latest defocus J.
In addition to IDFa, a planned defocus amount DF' during shutter movement is calculated. In #121, the number of pulses for driving the lens is calculated, and in #122, the lens is driven to the intended focus position when the shutter is running.

Below, #123. After performing the process of #124, shutter movement is performed, and thereby control is performed such that focusing is achieved during shutter movement. Exposure control is not related to the present invention, so a description thereof will be omitted.

(Effects of the Invention) As described above, in the present invention, the lens driving amount is calculated from the current defocus amount and the moving speed of the subject to make the defocus amount zero at the next focus detection, and In a camera with an automatic focus adjustment function and a tracking mode that drives the lens, if the current defocus amount is abnormal or unknown, tracking control is continued assuming that the current defocus amount is zero. This has the effect of reducing the risk of missing a photo opportunity and allowing you to always take photos that are close to being in focus.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic configuration of the present invention, FIG. 2 is a block circuit diagram of an embodiment of the present invention, FIG. 3 is a front view of a display section used in the same, and FIGS. 4 to 12 are A flowchart for explaining the operation of the same as above, and FIGS. 13 and 14 are diagrams for explaining the operation of the same. (1) is a focus detection means, (2) is a moving speed calculation means, (
3) is lens driven! Calculation means, (4) lens drive means, (5) focus determination means, and (6) release permission means. Figure 1

Claims (2)

[Claims] (1) Focus detection means that detects the focus state of the lens on the subject to be focused and outputs a signal indicating the amount of defocus, and a moving speed calculation that calculates the moving speed of the subject using the amount of defocus multiple times a lens drive amount calculation means for calculating a lens drive amount to make the defocus amount zero at the next focus detection from the current defocus amount and the moving speed of the subject; In the camera, the lens drive amount calculation means calculates, when the defocus amount detected by the focus detection means is larger than a predetermined value,
Alternatively, a camera with an automatic focus adjustment function, characterized in that when the focus detection means cannot detect the focus, the current defocus amount is set to zero to calculate the lens drive amount. (2) A focus determination means that determines whether the subject is in focus based on the focus detection result of the focus detection means, and a release permission means that authorizes a release request when it is determined that the subject is in focus. A camera with an automatic focus adjustment function according to claim 1, further comprising: